Method for verifying the authenticity of documents

ABSTRACT

The invention relates to a method for testing the authenticity of documents, in particular bank notes, documents of value or security documents, by authenticity criteria.  
     To increase the reliability of authenticity testing of documents, at least two different authenticity classes each with one or more authenticity criteria are provided, the individual authenticity classes differing in at least one authenticity criterion. An authenticity class is selected from the different authenticity classes and the document tested by the authenticity criteria of the selected authenticity class. The document is assigned the selected authenticity class if the document meets the authenticity criteria thereof.  
     This obtains higher reliability of authenticity testing since this method makes it possible to determine those documents that meet higher authenticity requirements, i.e. stricter authenticity criteria, than the other documents and are therefore authentic with higher probability.

[0001] This invention relates to methods and apparatuses for testing theauthenticity of documents, in particular bank notes, documents of valueor security documents, according to the generic part of the independentclaims.

[0002] Authenticity testing of documents is generally done by measuringcertain authenticity features, for example optical, electric or magneticfeatures, on a document under test and then testing the measuredauthenticity features with reference to given authenticity criteria. Forexample, the optical reflection behavior of the document is measured asan authenticity feature and it is then tested whether the measuredreflection behavior undershoots or exceeds a certain threshold value asthe associated authenticity criterion. Depending on the test result thedocument is classified as authentic or false.

[0003] The reliability of detecting forgeries can be increased forinstance by tightening the authenticity criteria in the testing ofcertain authenticity features, for example by raising or loweringthreshold values. In practice the authenticity criteria cannot betightened at will, however, since this would make the proportion ofauthentic documents not recognized as authentic—and possibly rejected ormisclassified—too high.

[0004] In bank note processing machines that are used in particular incommercial banks for deposit testing and clearing, this would lead forexample to elevated effort for postprocessing bank notes not recognizedas authentic by hand and possibly further by machine.

[0005] In authenticity testing in money-depositing machines, a generaltightening of authenticity criteria would mean that in particular usedor soiled authentic bank notes, whose authenticity features are lessdistinct due to soiling or damage compared to freshly printed banknotes, are not recognized as authentic and consequently rejected orwithheld as alleged forgeries, depending on the case of application.

[0006] The reliability in recognizing counterfeit bank notes istherefore limited by the required low proportion of authentic bank notesnot recognized as authentic. This is problematic especially whenforgeries are not recognized as such due to “loose” authenticitycriteria and return to circulation, for example after one customerdeposits counterfeit bank notes in self-service recycling machines andthe bank notes not identified as forgeries are then issued to othercustomers.

[0007] The method known from DE 196 18 541 A1 relates to determining asorting class from a number of bank note properties, such asdenomination, security features and soiling. Measuring results for thebank note properties are first mapped onto discrete classes and combinedin a class vector. The class vector is finally compared with individualrule vectors each corresponding to a certain sorting class. If the classvector of the bank note matches a rule vector, the bank note is assignedthe sorting class corresponding to the particular rule vector. Thismethod permits sorting classes to be determined fast and precisely.However, the derivation of a class for individual security features,i.e. the actual authenticity testing, is done by methods known from theprior art, so that the above-described problems also arise here when forexample a raising or lowering of threshold values for authenticityfeatures is intended to increase or reduce the reliability inauthenticity testing.

[0008] EP 0 101 115 A1 discloses a device for recognizing bank noteswherein a digital picture of the bank note is taken and compared with apreviously stored reference picture of a reference bank note. If a firstcomparison, in particular on one half of the bank note, does not yield asufficiently reliable result, the comparison can be repeated in otherareas of the bank note, for example with other comparative values.However, this opens up the possibility of selectively soiling ordamaging security-relevant areas of a counterfeit bank note to effect atest of other areas with possibly more easily imitated security featuresand thus—falsely—a positive test result.

[0009] It is the problem of the present invention to state methods andapparatuses for authenticity testing that permit documents to be testedwith elevated reliability, in particular without simultaneouslyincreasing the proportion of authentic documents falsely not recognizedas authentic.

[0010] This problem is solved by the authenticity testing methodsaccording to claims 1 and 14 and by the corresponding authenticitytesting apparatuses according to claims 18 and 21.

[0011] In the authenticity testing method according to claim 1, at leasttwo different authenticity classes each with one or more authenticitycriteria are provided, the individual authenticity classes differing inat least one authenticity criterion. For authenticity testing, anauthenticity class is selected from the different authenticity classesand the document tested by the authenticity criteria of the selectedauthenticity class. The document is assigned the selected authenticityclass if the document meets its authenticity criteria. The authenticitycriteria are for example threshold values or intervals for theauthenticity features used for testing. Authenticity features to be usedare for example optical, magnetic, electric or physical features, e.g.optical reflection, transmission or emission, magnetic permeability,electric conductivity, dielectric constant, thickness and format of thedocument as well as watermarks.

[0012] The invention is based on the idea of combining differentauthenticity criteria in authenticity testing of documents into aplurality of authenticity classes, the requirements for authenticityvarying in strictness depending on the authenticity class, since eachauthenticity class generally includes a different number of authenticitycriteria and/or authenticity criteria varying in strictness. If theauthenticity class selected has for example high requirements forauthenticity, e.g. very high threshold values for optical reflection ortransmission, the authenticity of documents meeting the authenticitycriteria of this selected authenticity class can be affirmed with highprobability. Documents not meeting the authenticity criteria of aselected authenticity class can be tested by other selected authenticityclasses with lower requirements for authenticity, for example lowerthreshold values, so that their authenticity can be affirmed withaccordingly lower probability. Altogether, this results in a division ofthe authenticity property, i.e. the measured authenticity features, ofthe documents under test into different authenticity classes. Thisdifferentiation of the result of authenticity testing makes it possibleto determine those documents that are authentic with higher probabilitythan in prior art authenticity testing methods, thereby altogetherincreasing the reliability of determining authenticity. Simultaneously,the other documents can still be tested by the hitherto usual—generally“less strict”—authenticity criteria, thereby keeping the proportion ofauthentic documents not recognized as authentic low.

[0013] In a development of the method, it is provided that the fitnessand/or denomination of the document is determined and the authenticityclass then selected in dependence on the fitness and/or denomination ofthe document. Denomination is the value or currency of the documentunder test. Fitness of the document is generally given by fitnessfeatures such as degree of soiling, limpness, damage, such as tears,holes or faulty places in the printed image, and foreign bodies, such asadhesive tape. For example, the authenticity class can be selected inthe authenticity testing of a document in dependence on the degree ofsoiling of the document, whereby clean and undamaged documents can betested by much stricter authenticity criteria, e.g. higher thresholdvalues, than very soiled or damaged documents. This clearly increasesthe reliability of recognizing forgeries in clean or slightly soileddocuments. Altogether, this fitness-dependent authenticity testingpermits documents with high fitness to be identified as authentic orfalse with high reliability. Since only the testing of documents withhigh fitness is tightened, the proportion of authentic documents notrecognized as authentic simultaneously remains low.

[0014] A further aspect of the invention is according to claim 14 that aportion of the authenticity criteria used for testing authenticity isdetermined on counterfeit documents. This extends authenticity testingwith defined authenticity criteria by additional authenticity testingwith additional authenticity criteria, the additional authenticitycriteria being determined on counterfeit documents. The additionalauthenticity criteria are generally determined in a separate method,e.g. in specially provided devices, wherein counterfeit documents aretested in particular for characteristic differences over authenticdocuments. Additional authenticity criteria are determined from thefound differences and then supplied to the authenticity testing method.Documents are still tested here by fixed authenticity criteria andclassified as authentic if they meet the authenticity criteria. Inaddition, forgeries can be recognized if the tested documents do notmeet the additional authenticity criteria determined on known forgeries,said criteria preferably relating to characteristic differences betweena found forgery and authentic documents. This achieves elevatedreliability in the recognition of forgeries, in particular with respectto known forgeries that are in circulation.

[0015] The invention will now be explained in more detail with referenceto examples shown in figures, in which

[0016]FIG. 1 shows the schematic structure of an apparatus for inventiveauthenticity testing of documents;

[0017]FIG. 2 shows the schematic structure of an authenticity testingsystem using authenticity criteria determined on counterfeit documents,and

[0018]FIG. 3 shows the schematic structure of a system for processingdeposited bank notes.

[0019]FIG. 1 shows the schematic structure of an apparatus for inventiveauthenticity testing of documents. Documents 10, for example bank notes,provided in input device 11 are removed singly from input device 11 andtransported with the aid of transport system 14 to output device 12.Here documents 10 are sorted into three different sorting classes andoutputted into corresponding output pockets 13. On the way between inputdevice 11 and output device 12 document 10 under test is transportedpast measuring device 15. Measuring device 15 measures the authenticityfeatures of document 10 under test. It optionally also measures fitnessfeatures characterizing the fitness of document 10. The dashed line inmeasuring device 15 is intended to indicate that measuring device 15 canhave two or optionally more components for separately measuringauthenticity and possibly fitness features. It is fundamentally alsopossible, however, to measure both authenticity and fitness featurestogether in one measuring device. In the shown example, measuring device15 only measures on one side of document 10 under test. However, theapparatus can generally also be designed so as to measure document 10from both sides, e.g. by two opposing measuring devices 15 through whichdocument 10 is transported.

[0020] Information about the features measured in measuring device 15 istransferred to evaluation device 16 where inventive authenticity testingis done. Selection of a certain authenticity class and its assignment todocument 10 under test are preferably realized by a computer program.The computer program tests for example whether an authenticity feature,e.g. optical reflection, measured on document 10 under test is greaterthan a threshold value for optical reflection belonging to the certainauthenticity class. If the test result is positive, document 10 isassigned the certain authenticity class, e.g. by writing a numbercharacterizing the authenticity class into a variable characterizing theauthenticity of document 10. If the test result is negative, thecomputer program continues testing the measured authenticity feature bylower threshold values belonging to other authenticity classes, i.e.less strict authenticity criteria, and assigns document 10 acorresponding authenticity class. Altogether, this results in a divisionof the authenticity property, i.e. the measured authenticity features,of documents 10 under test into different authenticity classes. If allthese tests deliver a negative test result, document 10 is classified asfalse.

[0021] In a preferred development of the method, the fitness of document10 is additionally determined from the measured fitness features.Document 10 is then assigned one of several fitness classescharacteristic of the particular fitness of the document under test.Bank note testing usually involves three fitness classes, namely unfit,fit and ATM-fit (very fit). The authenticity class is then selected insubsequent authenticity testing in dependence on the fitness classassigned to document 10 under test. ATM-fit bank notes are preferablysubjected to very strict authenticity criteria, while unfit or fit banknotes have to meet less strict authenticity criteria of otherauthenticity classes to still be classified as authentic. To increasethe reliability of authenticity testing, it is also possible to do anadditional authenticity test on documents 10 of a certain fitness class,for example fit or ATM-fit bank notes. Such an additional authenticitytest can be done for example on the basis of already measured data forindividual authenticity features.

[0022] Denomination can fundamentally likewise be determined viameasuring device 15 and evaluation device 16, but this might also bedone in separate measuring and evaluation devices.

[0023] In a typical sorting mode, for example for use in a bank noteprocessing machine for deposit testing and clearing, documents 10 aredivided into one or more sorting classes and outputted intocorresponding output pockets 13. Output device 12 is driven byevaluation device 16 such that a first one of output pockets 13 receivesbank notes—optionally of only one desired denomination—that are ATM-fit,were assigned an authenticity class with high requirements forauthenticity, i.e. strict authenticity criteria, and are in a desiredposition, i.e. a certain printed pattern is visible from above andoptionally aligned in a certain way. A second output pocket, theso-called reject pocket, receives those bank notes that could not beassigned an authenticity class and/or are not in a desired positionand/or optionally do not belong to the desired denomination. This outputpocket optionally also receives faultily drawn-in and/or transportedbank notes, e.g. double picks or folded bills. Finally, a third outputpocket receives all other bank notes, i.e. fit, unfit and ones that wereassigned an authenticity class with lower requirements for authenticity,i.e. less strict authenticity criteria. If for example a stack of banknotes of a certain denomination is inputted in a mixed position, thissorting mode permits those bank notes of a certain denomination to besorted out that are authentic with high probability, ATM-fit andsimultaneously have a desired position. Bank notes that meet thesecriteria can then be provided for immediate further output, e.g. in aself-service recycling machine.

[0024]FIG. 2 shows the schematic structure of an authenticity testingsystem using authenticity criteria determined on counterfeit documents.The mode of functioning of such a system differs from the example shownin FIG. 1 mainly in that the authenticity test done in evaluation device16 is performed in two steps. In a first step, the authenticity test isdone using authenticity criteria, which are preferably divided intoauthenticity classes. The authenticity class can be selected independence on the determined fitness of document 10 under test, asexplained above in connection with FIG. 1. If the measured authenticityfeatures meet the given authenticity criteria, document 10 is assignedthe corresponding authenticity class. In a second step of theauthenticity test, an additional test is done using authenticitycriteria determined on known counterfeit documents. Said authenticitycriteria are determined in bank note testing machines suitable for thispurpose, e.g. in a central bank or at a corresponding service provider.For reasons of data reduction there are preferably authenticity criteriathat are characteristic of the difference between a counterfeit and anauthentic document. The authenticity criteria used in the second step ofthe authenticity test are transferred in the shown example from controldevice 31, e.g. a server of a central bank or central service provider,over wire-bound or wireless connection 32 to one or more test stations30 simultaneously. The corresponding data can also be transferred bymeans of suitable data carriers, e.g. flash card, memory chips, floppy,CD or DVD. If a corresponding characteristic difference is nowascertained in the second step of the authenticity test, document 10 canbe identified as a forgery with high probability even if it meets theauthenticity criteria in the first step of the authenticity test. Thechronological order of the two steps can fundamentally be selected atwill.

[0025] Altogether, this system permits simple and fast updating offeatures and criteria for testing the authenticity of bank notes in anynumber of test stations 30 simultaneously, thereby guaranteeing highreliability in the recognition of counterfeit bank notes that are incirculation.

[0026]FIG. 3 shows the schematic structure of a system for applying theinventive authenticity testing. Documents 10, bank notes in thisexample, are deposited at commercial bank 39 by a depositor. The depositcan be made e.g. at the terminal of a self-service recycling machine. Intest station 30, which can be part of the terminal, the bank notes aretested for authenticity. If the bank notes meet the very strictauthenticity criteria of a selected authenticity class, they can beprovided for immediate further output, for example at the same terminal,other output terminals 34 and/or bank teller window 36. All bank notesthat do not meet these very strict authenticity criteria are supplied tocentral testing device 35, for example in central bank 40, to besubjected to further authenticity testing, this testing also usingso-called high-security features that guarantee especially reliablerecognition of counterfeit bank notes. Bank notes that meet thesecriteria can now be put back into circulation by being returned tocommercial bank 39 to be paid out at output terminals 34 or bank tellerwindow 36.

[0027] This example furthermore includes controller 31 in whichcounterfeit bank notes are used to determine additional authenticitycriteria—as stated above in the description for FIG. 2—that relate tocharacteristic differences between authentic bank notes and bank notesrecognized as forgeries in central testing device 35. The forgeries canbe transferred directly from testing device 35 to controller 31. Theauthenticity criteria determined there are then transferred overconnection 32 to test station 30 and can be used there optionally inaddition to the authenticity criteria divided into differentauthenticity classes —for testing the authenticity of bank notes.

[0028] To permit deposited forgeries to be retraced, characteristic dataof the deposited bank notes, e.g. printed images and/or serial numbers,can in addition be stored in control device 31 together with data on thedepositor, e.g. account number and/or personal identification number(PIN). If a bank note is recognized as a forgery in central testingdevice 35, characteristic data of the bank note, e.g. printed imagesand/or serial numbers, are transferred to control device 31. There,comparison of the stored data with the transferred data permits thedepositor of the counterfeit bank note to be identified. Controller 31can either be installed inside commercial bank 39, as shown, or belocated outside the same, for example at a central service provider.

[0029] The system shown in FIG. 3 deals by way of example with theapplication of the inventive method for testing the authenticity of banknotes in a depositing machine at a commercial bank. However, theauthenticity testing can fundamentally also be done in a bank noteprocessing machine in which bank notes are inputted by an employee fortesting and/or sorting, e.g. after being deposited at the teller windowof a commercial bank. The authenticity testing and the subsequent courseof the method involving sorting, reissue and/or transfer for testing ina central bank are analogous.

1. A method for testing the authenticity of documents wherein a document(10) is tested by authenticity criteria, characterized in that at leasttwo different authenticity classes each with one or more authenticitycriteria are provided, the individual authenticity classes differing inat least one authenticity criterion, so that requirements forauthenticity vary in strictness depending on the authenticity class, anauthenticity class is selected from the different authenticity classesand the document (10) tested by the authenticity criteria of theselected authenticity class, and the document (10) is assigned theselected authenticity class if the document (10) meets the authenticitycriteria thereof.
 2. A method according to claim 1, characterized inthat if the authenticity criteria of the selected authenticity class arenot met a further authenticity class is selected and the authenticitytesting repeated by the authenticity criteria of the selected furtherauthenticity class.
 3. A method according to any of the above claims,characterized in that the fitness and/or denomination of the document(10) is determined and the authenticity class then selected independence on the fitness and/or denomination of the document (10).
 4. Amethod according to claim 3, characterized in that the fitness of thedocument (10) is dividable into fitness classes, the document (10) isassigned a fitness class corresponding to the fitness and theauthenticity class for testing the authenticity of the document (10) isselected in dependence on the fitness class assigned to the document(10).
 5. A method according to any of the above claims, characterized inthat the individual documents (10) are sorted in accordance with theparticular assigned authenticity class.
 6. A method according to claim5, characterized in that the individual documents (10) are sortedadditionally in accordance with their fitness, optionally their fitnessclass, and/or their denomination.
 7. A method according to either ofclaims 5 and 6, characterized in that the documents (10) are sorted andthereby divided into one or more sorting classes, a first sorting classreceiving the documents (10) that have high fitness (ATM-fit), wereassigned a certain authenticity class and are in a desired positionand/or belong to a desired denomination.
 8. A method according to claim7, characterized in that a second sorting class receives the documents(10) that were not assigned any of the authenticity classes and/or arenot in the desired position and/or do not belong to a desireddenomination.
 9. A method according to claim 8, characterized in that athird sorting class receives all other documents (10) not divided intothe first or second sorting class.
 10. A method according to any ofclaims 7 to 9, characterized in that the documents (10) divided into thefirst sorting class are provided for a further immediate use.
 11. Amethod according to either of claims 9 and 10, characterized in that thedocuments (10) divided into the third sorting class are transferred to atesting device (35) and subjected there to further authenticity testing,in particular using further authenticity criteria.
 12. A methodaccording to claim 11, characterized in that those of the documents (10)tested in the central testing device (35) that are fit or ATM-fit andmeet the authenticity criteria of authenticity testing in the centraltesting unit (35) are provided for a further use.
 13. A method accordingto any of the above claims, characterized in that the documents (10) areinputted by a depositor and supplied to authenticity testing, and dataidentifying the depositor and characteristic data of the inputteddocuments (10) are stored together.
 14. A method for testing theauthenticity of documents, in particular according to any of the aboveclaims, wherein a document (10) is tested by authenticity criteria, andthe document (10) is classified as authentic if the authenticitycriteria are met, characterized in that at least a portion of theauthenticity criteria used for authenticity testing is determined oncounterfeit documents (10).
 15. A method according to claim 14,characterized in that the authenticity testing is performed in a teststation (30) and at least one portion of the authenticity criteria usedfor authenticity testing in the test station (30) is determined in acontrol device (31) on counterfeit documents (10).
 16. A methodaccording to claim 15, characterized in that information about theauthenticity criteria determined on counterfeit documents (10) istransferred from the control device (31) to the test station (30).
 17. Amethod according to claim 16, characterized in that the informationtransferred from the control device (31) to the test station (30)relates to characteristic differences between a counterfeit and anauthentic document (10).
 18. An apparatus for testing the authenticityof documents, in particular bank notes, documents of value or securitydocuments, having at least one measuring device (15) for measuring atleast one authenticity feature on a document (10) under test, and atleast one evaluation device (16) for testing the measured authenticityfeature by authenticity criteria, characterized in that the evaluationdevice (16) is formed for testing the authenticity of the document (10)by authenticity criteria of an authenticity class selected from aplurality of different authenticity classes, whereby the authenticityclasses each include one or more authenticity criteria and differ in atleast one authenticity criterion, so that requirements for authenticityvary in strictness depending on the authenticity class, and the document(10) is assigned the selected authenticity class if the document (10)meets the authenticity criteria thereof.
 19. An apparatus according toclaim 18, characterized in that the measuring device (15) is formed formeasuring at least one fitness feature that characterizes the fitness ofa document (10) under test, and the evaluation device (16) is formed fordetermining the fitness of the document (10) from the measured fitnessfeature and for selecting the authenticity class in dependence on thedetermined fitness of the document (10).
 20. An apparatus according toeither of claims 18 and 19, characterized in that an output device (12)is provided for outputting documents (10) sorted according toauthenticity class and/or fitness and/or denomination.
 21. An apparatusfor testing the authenticity of documents, in particular bank notes,documents of value or security documents, having at least one measuringdevice (15) for measuring at least one authenticity feature on adocument (10) under test, and at least one evaluation device (16) fortesting the measured authenticity feature by authenticity criteria,characterized in that the evaluation device (16) is formed for testingthe authenticity of the document (10) by authenticity criteriadetermined on counterfeit documents (10).
 22. An apparatus according toclaim 21, characterized in that a control device (31) is provided thatis formed for determining the authenticity criteria on counterfeitdocuments (10) and from which information on the authenticity criteriadetermined on counterfeit documents (10) is transferable to theevaluation device (16).